[ew] Simplify the entry watcher logic.

chrome/browser/extensions/api/file_system/entry_watcher_service_factory.h

-// Copyright 2014 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef CHROME_BROWSER_EXTENSIONS_API_FILE_SYSTEM_ENTRY_WATCHER_SERVICE_FACTORY_H_
-#define CHROME_BROWSER_EXTENSIONS_API_FILE_SYSTEM_ENTRY_WATCHER_SERVICE_FACTORY_H_
-
-#include "base/memory/singleton.h"
-#include "components/keyed_service/content/browser_context_keyed_service_factory.h"
-
-namespace content {
-class BrowserContext;
-}  // namespace content
-
-namespace extensions {
-
-class EntryWatcherService;
-
-// Creates instances of the EntryWatcherService class.
-class EntryWatcherServiceFactory : public BrowserContextKeyedServiceFactory {
- public:
-  // Returns a service instance singleton per |context|, after creating it
-  // (if necessary).
-  static EntryWatcherService* Get(content::BrowserContext* context);
-
-  // Returns a service instance for the context if exists. Otherwise, returns
-  // NULL.
-  static EntryWatcherService* FindExisting(content::BrowserContext* context);
-
-  // Gets a singleton instance of the factory.
-  static EntryWatcherServiceFactory* GetInstance();
-
- private:
-  friend struct DefaultSingletonTraits<EntryWatcherServiceFactory>;
-
-  EntryWatcherServiceFactory();
-  ~EntryWatcherServiceFactory() override;
-
-  // BrowserContextKeyedServiceFactory overrides:
-  KeyedService* BuildServiceInstanceFor(
-      content::BrowserContext* profile) const override;
-  bool ServiceIsCreatedWithBrowserContext() const override;
-
-  DISALLOW_COPY_AND_ASSIGN(EntryWatcherServiceFactory);
-};
-
-}  // namespace extensions
-
-#endif  // CHROME_BROWSER_EXTENSIONS_API_FILE_SYSTEM_ENTRY_WATCHER_SERVICE_FACTORY_H_